Hi,

 

I'm building a Quad from sketch.

My goals are-

it needs to be stable,

it needs to carry a heavy DSLR

therefore i will go BIG. say around 80-100CM.

 

I'd like to get guidelines for choosing the motors.

rather higher or lower KV/(rpm/v) ?

small propellers with big pitch ? or large propellers with small pitch ?

 

any other tips for choosing motors and propellers ?

 

how about ducted fans ?

if i were to use 4 ducted fans instead propellers - is there a reason that all QUADs use propellers and not ducted fans ?

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I don't know much about this yet, but I think that the reason that they don't use ducted fans is that the fan uses a lot of battery and can't adjust to throttle changes quickly enough.

really? because the blades are very small ?

i will try with a 100mm ducted fan which is relatively large, hope i have luck with it.

 

still, i want the propellers version as well, any guidelines ?

The reason EDFs are not used is because you cannot obtain CW and CCW variants. Without this the quad rotates around the yaw axis at the combined velocity of all the EDFs at once. Hover = slowly, WOT = fast. No counter rotation no point in trying to be accurate.

As for sizing especially that big I have no idea.

thanks.

does it means that quads usually combine CW and CCW propellers ?

can you expand on this ? what rotors are CW and what are CCW ?

also, i guess that they just have the propeller mounted backwards and the motor spinning in the opposite direction, resulting in all motors pushing air downwards after all, am i correct ?

Quads usually switch off cw ccw cw ccw props and to turn they speed up an slow down certain groups. Also alot of edf that I have seen have stators that make the air from the prop of the fan zero torque. Still edf also can't adjust to rapid changes off speed so it would be hard to control and unstable. There are special props designed to turn ccw along with other props that are cw.

oh i see...

OK plan is changing...

 

I couldn't find such props. when i found one, it didn't have its brother with the clockwise version.

I think of just installing the motors facing down and spinning them counter clockwise.

that might do it - no ?

 

is there some basic guidelines or tutorial about quads designing ?

It is possible to use EDF's but as stated here any many other posts. EDF's are not fast enough to reach speed changes and that way you cannot get good and accurate control of your quad. EDF quad's are always a bit wobbly to fly.

 

Whole EDF is based on idea to maximize airflow in a "turbine" tunnel. Quad control then again needs really accurate airflow control

 

Here is a really good video of EDF quad... Like they say, picture is worth of 1000 words and video is worth for million words.

 

Low KV motors with big propellers are always good combination for quads.

for big payload is low kv motors and big propellers ok?

oh crap.. at the last second of the vid....

 

anyways i found the guide  http://code.google.com/p/arducopter/wiki/ArduCopter_Quad

 

and here are the props:
http://store.jdrones.com/ProductDetails.asp?ProductCode=ac1245comp&...

i guess i won't find bigger than that...

do you suggest choosing a higher KV motors than these that are basically suggested for these props for arducopter (880KV) ?

say 1800 KV motors then i'll use less throttle...

Keep in mind that KV doesn't say anything about the power of the engine. It defines how many rpm it will make per volt. The power of the engine is expressed in watt.
I am in doubt about a 750kv and a 860kv which can deliver about the same amouth of power.

yea sure.

what you guys say about this one ?

http://cgi.ebay.com/C2836-KV1120-Brushless-Motor-Blue-Silver-airpla...

it's the same one JDrones is selling, just this one is 1120KV instead of 880KV.

current rating is also a bit higher.

I think i'll choose it.

 

in case i won't have enough power with the four rotors with heavy load,

i could use the ducted fan i already ordered, ill put it on the bottom, and that could be a 'boost' motor for fast ascending with heavy load. i know the torque will cause yaw, but this is just for the vertical ascending boost....

For 12" props, don't go over 1000 Kv or you end up burning your Motors/ESC's etc.

 

Those ArduCopter motors are not actually same that are sold on market. They are modified to our project use.

 

All ArduCopter motors are optimized to 50-75% power levels. And every single motor that are installed on jDrones Assembled kits goes trough test and their RPM's etc are checked. That way perfect motor match can be guaranteed.

 

Here is some real and tested thrust data from AC2836-358 motors:

12x45 ArduCopter propellers, 3S LiPo was used on test, Motors can be used with 4S too

Power 25%:

1.5Amp

17.5W

230gr

 

Power 50%:

6.1Amp

70W

650gr

 

Power 75%

14.2Amp

160W

1290gr

 

Power 100%

20Amp

210W

1380gr

 

Same motor with AC10x45 Prop:

Power 25%

1.2Amp

14W

200gr

 

Power 50%

4.2Amp

46W

485gr

 

Power 75%

9.6Amp

98W

860gr

 

Power 100%

12.5Amp

126W

1010gr

 

PS. When we originally looked a motor manufacturer and motors for ArduCopter project, we also tested these blue silvers.... Well, there are better ones available....

 

We spent about 4 months on looking motors for ArduCopter use and during that time we created rather big graveyard of BL-Motors.

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